It is known to provide a connection between an accelerator pedal and a throttle plate of a throttle mechanism using a Bowden cable. The accelerator pedal can be formed in one or more parts and is conventionally mounted in a floor assembly of the driver cell of a motor vehicle. The throttle plate is opened by the driver's foot pressure on the accelerator pedal. One or two resetting springs are provided to draw the accelerator pedal and thus the throttle plate back to an idling position when the driver's foot is lifted. In this way a link is provided between the pedal and throttle plate position on the one hand and a change in the engine speed on the other hand.
As a result of the introduction of new combustion engines with improved exhaust and fuel consumption properties there is an increasing need to supply electronic engine systems with an electronic signal representing accelerator position. It is known to cause pedal movement to be converted into an electronic engine management signal This is often referred to as `drive by wire`. However in order to produce the correct `feel` which the driver is used to experience through the foot when driving a car with a Bowden cable linkage, it is necessary to produce, in a drive by wire system, a resistance to pedal movement which simulates the resistance and the same driving conditions which would have been produced using a cable linkage system.
Pedal mechanisms are known wherein the friction force is produced by means of separate pretensioned friction elements (e.g. DE 3 411 456 C2). Arrangements of this kind are complicated in construction and limiting for the size of the friction force. It is also important that if one spring breaks then a satisfactory and safe resetting must be possible. The safe resetting in the event of a spring breaking is an absolute necessity for reasons of product liability and is a legal requirement in the USA through safety standard FMVSS124.
There are already several proposals (e.g. DE 3 411 393 A1; EP A 0 092 640; WO A 89/07706; WO A 91/04165) where additional friction, spring and connecting elements are provided to produce the friction.
A arrangement is known from the German Patent Application DE 4 407 005 C1 where the friction is produced by pretensioning a friction mechanism through reset springs. A complicated large-scale transfer mechanism is used here and a radially displaceable wedge-shaped friction element is used to produce friction on a lever rigidly coupled to the pedal axis.
This arrangement requires several parts movable relative to each other and cannot be integrated in the pedal structure as a result of the large installation space required.
The invention therefore seeks to provide a pedal mechanism which transfers the pedal position simply and precisely to for example an electronic engine control unit whilst the driving feel remains unchanged compared to conventional regulating processes.
An object of the invention is to design a pedal mechanism so that the resetting force of the resetting elements is used directly to produce the friction force. Furthermore the friction mechanism is to be capable of integration in the pedal so that no additional structural or sealing elements are required to protect the friction mechanism from dirt. Furthermore the pedal bearing should be precise with neutral wear and able to be manufactured cost-effectively. The unavoidable wear to the highly-stressed friction faces producing the pedal friction required for reasons of comfort should not change the play or accuracy of the pedal mechanism throughout its service life.